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Early speculation about nuclear weapons assumed that an "atom bomb" would be a large amount of fissile material moderated by a neutron moderator, similar in structure to a nuclear reactor or "pile". [11] Only the Manhattan Project embraced the idea of a chain reaction of fast neutrons in pure metallic uranium or plutonium.
"Graphite reactor" directs here. For the graphite reactor at Oak Ridge National Laboratory, see X-10 Graphite Reactor. A graphite-moderated reactor is a nuclear reactor that uses carbon as a neutron moderator, which allows natural uranium to be used as nuclear fuel. The first artificial nuclear reactor, the Chicago Pile-1, used nuclear graphite ...
This poses a problem for nuclear reactor vessels and significantly limits their lifetime (which can be somewhat prolonged by controlled annealing of the vessel, reducing the number of the built-up dislocations). Graphite neutron moderator blocks are especially susceptible to this effect, known as Wigner effect, and
A neutron's energy can vary widely, but it is not uncommon to have energies up to and exceeding 10 MeV (10,000,000 eV) in the centre of a nuclear reactor. A neutron with a significant amount of energy will create a displacement cascade in a matrix via elastic collisions. For example, a 1 MeV neutron striking graphite will create 900 ...
Reactors in which neither the moderator nor the coolant is a liquid (e.g., a graphite-moderated, gas-cooled reactor) will have a zero void coefficient. It is unclear how the definition of "void" coefficient applies to reactors in which the moderator/coolant is neither liquid nor gas (supercritical water reactor).
An attempt to use an extendable robot to remove a fragment of melted fuel from a wrecked reactor at Japan’s tsunami-hit Fukushima Daiichi nuclear power plant was suspended Thursday due to a ...
Nuclear reactors with water moderator require at least some enrichment of 235 U. Nuclear reactors with heavy water or graphite moderation can operate with natural uranium, eliminating altogether the need for enrichment and preventing the fuel from being useful for nuclear weapons; the CANDU power reactors used in Canadian power plants are an ...
A pressurized heavy-water reactor (PHWR) is a nuclear reactor that uses heavy water (deuterium oxide D 2 O) as its coolant and neutron moderator. [1] PHWRs frequently use natural uranium as fuel, but sometimes also use very low enriched uranium .